const int LEDPin = 13;
int interval = 1000;
unsigned long previousMillis = 0;
int LEDstate = LOW;
void setup()
{
   pinMode(LEDPin,OUTPUT);
}

void loop()
{
   unsigned long currentMillis = millis();
  if(currentMillis - previousMillis > interval)
 {
    previousMillis = currentMillis;
    if(LEDstate = LOW)
    LEDstate = HIGH;
    else
    LEDstate = LOW;
    
    digitalWrite(LEDPin,LEDstate);
 } 
}
